What is the prudentially right thing to do in situations in which our actions will shape our preferences? Suppose, for instance, that you are considering getting married, and that you know that if you get married, you will prefer being unmarried, and that if you stay unmarried, you will prefer being married. This is the problem I will deal with in this article. I will begin by explaining why preferences matter to prudence. I will then go on to discuss a couple of unsuccessful theories and see what we can learn from their mistakes. One of the most important lessons is that how you would have felt about a life had you never led it is irrelevant to the question of what you prudentially ought to do. My theory takes this into account. What counts is how you feel about a life when you are actually leading it. (Published Online August 21 2006).